1. Field of the Invention
The present invention relates to a technique for controlling data transfer among equipments connected to a network. More specifically, the present invention relates to method and apparatus of data transfer controlling data transfer when a plurality of equipments having different protocols, command sets and the like are connected to a network, as well as to a medium recording the data transfer program.
2. Description of the Background Art
Along with widespread used of the Internet various application protocols used on the Internet have been developed. One of such application protocols is FTP (File Transfer Protocol) used on UNIX (registered trademark of AT&T).
FTP is an application protocol operating on IP (Internet Protocol) as a lower layer, aimed to enable sharing of files, and it enables effective implementation of reliable data transfer while not revealing differences among various file systems. Basically, FTP is for transmitting/receiving a set of statistically recorded files, that is, data of which contents do not change with time between computers. FIG. 1 is a screen shot representing an exemplary use of the FTP (a screen shot of FTP Explorer on Windows 95 (registered trademark of Microsoft)).
In EPG (Electric Program Guide) selecting and receiving a title or the like of broadcast programs, characters or icons representing titles, channels and the like are displayed on a screen, and when a title or a channel is selected by a remote controller or the like, corresponding broadcast starts. This corresponds to selection of data from hierarchical menu of a cable television, for example. In this case, the data is stream data of digital broadcast transmitted together with time information. Therefore, the data is of different nature from the data of the files such as described above which are stored and can be received at any time.
According to FTP described above, what is necessary is simply to transmit a file from a transmitting side computer to a receiving side computer, and therefore only one type of transfer method is used. According to EPG, when a broadcast channel is selected by a tuner of the receiving side, stream data corresponding to the channel is received by the tuner. In the reception of the stream data, only one type of transfer method is used. It should be noted, however, that different data format is used dependent on the type of the data to be transmitted, that is, music, data or video images, for example.
In this manner, even when there are a plurality of data forms to be transmitted/received by equipments connected to the network, transmission/reception for the file or for the stream data only has been done, dependent on whether the object of access is a file or stream data. More specifically, there has been no problem in file transfer between computers or reception of TELEVISION programs in the prior art where the method of transfer is uniquely determined dependent on the application. When various equipments including a personal computer, an audio visual equipment and other home use electric equipments are connected to a network, however, the data transmitted/received within the network include various data of different natures, such as files, stream data of reception data of TELEVISION broadcast, commands controlling equipments connected to the network, user interface information and so on. Therefore, it is impossible to uniquely determine the method of transfer, making data transmission/reception difficult.
In transmitting/receiving motion picture data, different command sets may be used among a tuner for receiving broadcast, a DVD (Digital Versatile Disc), a VCR (Video Cassette Recorder) and so on, and an appropriate command set must be selected for transmitting/receiving motion picture data through the network. In order to transmit/receive data of different natures, it is necessary to use different applications, different protocols and to select different command set, and there has been no method allowing integral handling of such data having different natures.
Japanese Patent Laying-Open Nos. 5-176010, 5-153185 and 9-284567 disclosed related techniques.
According to the invention disclosed in Japanese Patent Laying-Open No. 5-176010, when an integrated document is to be transferred through a telephone network, a protocol is automatically selected for transfer processing, based on an identifier of each file constituting the integrated document. The protocol is selected, however, not considering protocols which can be handled by the receiving side equipment, but based on the nature of the file to be transferred by the transmitting side equipment.
According to the invention disclosed in Japanese Patent Laying-Open No. 5-153185, when an application program of a first node and an application program of a second node exchange data and protocols assumed by respective application programs differ, a protocol compensating function compensates for the difference. The compensating function enables development of an application program not taking into account the protocol of the counterpart or object of transmission, and it becomes unnecessary for the user to recognize difference in protocols. It is necessary, however, to prepare the compensating function for all possible combinations of the protocols. This makes the compensation function complicated.
According to the invention disclosed in Japanese Patent Laying-Open No. 9-284567, a server receives attribute information representing a protocol, a communication transfer rate and the like from a terminal through a network, and notices to an encoder. Based on the attribute information, the encoder encodes voice information, image information or the like having real-time nature, and thereafter, the server transmits the coded information to the terminal through the network. More specifically, the invention relates to a technique for encoding data having real-time nature using an encoder, so as to ensure appropriate transfer rate. This reference, however, does not describe any technique related to files not containing time information or switching of command sets for controlling equipments.
Even when the prior art technique described above are used, a method of integrally handling data of different natures described above cannot be realized.